FBMYSQLD_MULTIFR

NAME

mysqld_multi - manage multiple MySQL servers

SYNOPSIS

mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

DESCRIPTION

mysqld_multi

is designed to manage several
mysqld
processes that listen for connections on different Unix socket files and TCP/IP ports. It can start or stop servers, or report their current status. The MySQL Instance Manager is an alternative means of managing multiple servers (see
mysqlmanager(8)).

mysqld_multi
searches for groups named
[mysqldN]
in
my.cnf
(or in the file named by the
--config-file
option).
N
can be any positive integer. This number is referred to in the following discussion as the option group number, or
GNR. Group numbers distinguish option groups from one another and are used as arguments to
mysqld_multi
to specify which servers you want to start, stop, or obtain a status report for. Options listed in these groups are the same that you would use in the
[mysqld]
group used for starting
mysqld. (See, for example,
Section 2.12.1.2, "Starting and Stopping MySQL Automatically".) However, when using multiple servers, it is necessary that each one use its own value for options such as the Unix socket file and TCP/IP port number. For more information on which options must be unique per server in a multiple-server environment, see
Section 5.6, "Running Multiple MySQL Servers on the Same Machine".

To invoke
mysqld_multi, use the following syntax:

shell> mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

start,
stop, and
report
indicate which operation to perform. You can perform the designated operation for a single server or multiple servers, depending on the
GNR
list that follows the option name. If there is no list,
mysqld_multi
performs the operation for all servers in the option file.

Each
GNR
value represents an option group number or range of group numbers. The value should be the number at the end of the group name in the option file. For example, the
GNR
for a group named
[mysqld17]
is
17. To specify a range of numbers, separate the first and last numbers by a dash. The
GNR
value
10-13
represents groups
[mysqld10]
through
[mysqld13]. Multiple groups or group ranges can be specified on the command line, separated by commas. There must be no whitespace characters (spaces or tabs) in the
GNR
list; anything after a whitespace character is ignored.

This command starts a single server using option group
[mysqld17]:

shell> mysqld_multi start 17

This command stops several servers, using option groups
[mysqld8]
and
[mysqld10]
through
[mysqld13]:

shell> mysqld_multi stop 8,10-13

For an example of how you might set up an option file, use this command:

shell> mysqld_multi --example

As of MySQL 5.1.18,
mysqld_multi
searches for option files as follows:

•
With
--no-defaults, no option files are read.

•
With
--defaults-file=file_name, only the named file is read.

•
Otherwise, option files in the standard list of locations are read, including any file named by the
--defaults-extra-file=file_name
option, if one is given. (If the option is given multiple times, the last value is used.)

Before MySQL 5.1.18, the preceding options are not recognized. Files in the standard locations are read, and any file named by the
--config-file=file_name
option, if one is given. A file named by
--config-file
is read only for
[mysqldN]
option groups, not the
[mysqld_multi]
group.

Option files read are searched for
[mysqld_multi]
and
[mysqldN]
option groups. The
[mysqld_multi]
group can be used for options to
mysqld_multi
itself.
[mysqldN]
groups can be used for options passed to specific
mysqld
instances.

As of MySQL 5.1.35, the
[mysqld]
or
[mysqld_safe]
groups can be used for common options read by all instances of
mysqld
or
mysqld_safe. You can specify a
--defaults-file=file_name
option to use a different configuration file for that instance, in which case the
[mysqld]
or
[mysqld_safe]
groups from that file will be used for that instance. Before MySQL 5.1.35, some versions of
mysqld_multi
pass the
--no-defaults
options to instances, so these techniques are inapplicable.

mysqld_multi
supports the following options.

•
--help

Display a help message and exit.

•
--config-file=file_name

As of MySQL 5.1.18, this option is deprecated. If given, it is treated the same way as
--defaults-extra-file, described earlier.
--config-file
is removed in MySQL 5.5.

Before MySQL 5.1.18, this option specifies the name of an extra option file. It affects where
mysqld_multi
looks for
[mysqldN]
option groups. Without this option, all options are read from the usual
my.cnf
file. The option does not affect where
mysqld_multi
reads its own options, which are always taken from the
[mysqld_multi]
group in the usual
my.cnf
file.

•
--example

Display a sample option file.

•
--log=file_name

Specify the name of the log file. If the file exists, log output is appended to it.

•
--mysqladmin=prog_name

The
mysqladmin
binary to be used to stop servers.

•
--mysqld=prog_name

The
mysqld
binary to be used. Note that you can specify
mysqld_safe
as the value for this option also. If you use
mysqld_safe
to start the server, you can include the
mysqld
or
ledir
options in the corresponding
[mysqldN]
option group. These options indicate the name of the server that
mysqld_safe
should start and the path name of the directory where the server is located. (See the descriptions for these options in
mysqld_safe(1).) Example:

[mysqld38]
mysqld = mysqld-debug
ledir = /opt/local/mysql/libexec

•
--no-log

Print log information to
stdout
rather than to the log file. By default, output goes to the log file.

•
--password=password

The password of the MySQL account to use when invoking
mysqladmin. Note that the password value is not optional for this option, unlike for other MySQL programs.

•
--silent

Silent mode; disable warnings.

•
--tcp-ip

Connect to each MySQL server through the TCP/IP port instead of the Unix socket file. (If a socket file is missing, the server might still be running, but accessible only through the TCP/IP port.) By default, connections are made using the Unix socket file. This option affects
stop
and
report
operations.

•
--user=user_name

The user name of the MySQL account to use when invoking
mysqladmin.

•
--verbose

Be more verbose.

•
--version

Display version information and exit.

Some notes about
mysqld_multi:

•
Most important: Before using
mysqld_multi
be sure that you understand the meanings of the options that are passed to the
mysqld
servers and
why
you would want to have separate
mysqld
processes. Beware of the dangers of using multiple
mysqld
servers with the same data directory. Use separate data directories, unless you
know
what you are doing. Starting multiple servers with the same data directory does
not
give you extra performance in a threaded system. See
Section 5.6, "Running Multiple MySQL Servers on the Same Machine".

•

Important
Make sure that the data directory for each server is fully accessible to the Unix account that the specific
mysqld
process is started as.
Do not
use the Unix
root
account for this, unless you
know
what you are doing. See
Section 5.3.6, "How to Run MySQL as a Normal User".

•
Make sure that the MySQL account used for stopping the
mysqld
servers (with the
mysqladmin
program) has the same user name and password for each server. Also, make sure that the account has the
SHUTDOWN
privilege. If the servers that you want to manage have different user names or passwords for the administrative accounts, you might want to create an account on each server that has the same user name and password. For example, you might set up a common
multi_admin
account by executing the following commands for each server:

See
Section 5.4, "The MySQL Access Privilege System". You have to do this for each
mysqld
server. Change the connection parameters appropriately when connecting to each one. Note that the host name part of the account name must permit you to connect as
multi_admin
from the host where you want to run
mysqld_multi.

•
The Unix socket file and the TCP/IP port number must be different for every
mysqld. (Alternatively, if the host has multiple network addresses, you can use
--bind-address
to cause different servers to listen to different interfaces.)

•
The
--pid-file
option is very important if you are using
mysqld_safe
to start
mysqld
(for example,
--mysqld=mysqld_safe) Every
mysqld
should have its own process ID file. The advantage of using
mysqld_safe
instead of
mysqld
is that
mysqld_safe
monitors its
mysqld
process and restarts it if the process terminates due to a signal sent using
kill -9
or for other reasons, such as a segmentation fault. Please note that the
mysqld_safe
script might require that you start it from a certain place. This means that you might have to change location to a certain directory before running
mysqld_multi. If you have problems starting, please see the
mysqld_safe
script. Check especially the lines:

The test performed by these lines should be successful, or you might encounter problems. See
mysqld_safe(1).

•
You might want to use the
--user
option for
mysqld, but to do this you need to run the
mysqld_multi
script as the Unix
root
user. Having the option in the option file doesn't matter; you just get a warning if you are not the superuser and the
mysqld
processes are started under your own Unix account.

The following example shows how you might set up an option file for use with
mysqld_multi. The order in which the
mysqld
programs are started or stopped depends on the order in which they appear in the option file. Group numbers need not form an unbroken sequence. The first and fifth
[mysqldN]
groups were intentionally omitted from the example to illustrate that you can have
"gaps"
in the option file. This gives you more flexibility.

COPYRIGHT

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.

SEE ALSO

For more information, please refer to the MySQL Reference Manual,
which may already be installed locally and which is also available
online at http://dev.mysql.com/doc/.